Peripherally inserted central catheter with continuous central venous oximetry and proximal high flow port

ABSTRACT

A peripherally inserted central catheter includes three lumens that communicate with its proximal end. A large lumen terminates short of the distal end of the catheter and is used for the infusion of fluids into the venous system. A second lumen terminates at the distal end and is suitable for measuring blood pressure in the central venous system and infusion of fluids into the central venous system. The third lumen houses a pair of optical fibers which form part of a central venous oxygen saturation (S v O 2 ) monitoring system.

BACKGROUND OF THE INVENTION

The field of the invention is catheters, and in particular cathetersinserted into the central venous system.

Oxygen is essential to human life. An immediate cascade of pathologicprocesses is triggered in response to a decrease in oxygen delivery.Since oxygen is not stored in sufficient quantities in the body,inadequate oxygen transport to the cells for even very brief periods oftime can result in organ failure and death. Thus our ability to monitorand increase oxygen delivery to the body is essential to preventing andreversing organ dysfunction (such as heart, kidney and liver failure orcoma) and death. The goal is to balance oxygen supply with tissue oxygendemand.

In an effort to properly balance oxygen supply and demand a number ofmeasurements are commonly made. Current monitoring techniques includecontinuous electrocardiographic monitoring, measurement of bloodpressure, measurement of skin temperature and capillary refill. Thesenoninvasive techniques provide little information regarding hemodynamicstatus and/or oxygen delivery to the brain or body (tissue).

Mixed venous oxygen saturation (SvO₂) is the amount of oxygen in bloodtaken from a vessel coming from the right side of the heart going intothe lungs. This reflects the amount of oxygen being delivered to thetissues. When oxygen delivery to the tissues is inadequate, the SvO₂ islow. When oxygen delivery to the tissues is adequate, the SvO₂ is normalor high. This is the physiological basis for using SvO₂ as the earliestindicator of response to therapy during patient treatment.

Ideally, SvO₂ is drawn from a pulmonary artery catheter which isapproximately 100 centimeters long and is placed into a vein thataccesses the right side of the heart and then into the pulmonary artery.However, placement of a pulmonary artery catheter is extremely difficultand can be impractical during cardiac arrest and severe shock due to lowblood pressure and may actually increase patient mortality.

The central venous system avoids traversing the heart and can be moreeasily accessed. Thus, a number of studies have supported thesubstitution of central venous (right atrial or superior vena cava)oxygen saturation (ScvO₂) for pulmonary artery blood oxygen saturation(SvO₂). The central venous blood can be obtained much more easily thanblood from the pulmonary artery because the heart does not need to betraversed.

Central venous measurement of oxygen saturation (SvO₂) is currentlyachieved by puncture of the central venous circulation (CVC) system(i.e., internal jugular vein, subclavian vein or femoral vein) andinsertion of an intravascular catheter device such as that disclosed inU.S. Pat. No. 5,673,694. Such CVC catheters employ fiber optics tomeasureSvO₂ as described, for example, in U.S. Pat. Nos. 5,754,716 and4,711,522. They are relatively short (i.e., less than 30 cm in length)and inflexible devices which can remain in place for only a short time(e.g., generally less than 7 days).

The use of CVC catheters to measure oxygen saturation and blood pressurefrom the superior vena cava or right atrium has a number of drawbacks.These CVC catheter insertions are known to be associated withcomplications of lung puncture (pneumothorax), major hemorrhage, neckhematoma, carotid artery puncture, cardiac dysrhythmias and infection.In addition, because they can remain in place for only a short time,repeated insertions are necessary when monitoring is required over along time period.

Peripherally inserted central venous catheters have been available formany years to administer fluids such as parenteral nutrition,chemotherapy, vasopressor (adrenalin like medications), antibiotics andother hypertonic/caustic solutions. These catheters are also used forblood draws. These catheters are inserted into peripheral veins(generally the antecubital, basilic or cephalic veins) and advanced intothe central (deep) venous system with the tip ideally positioned in thesuperior vena cava or right atrium thus allowing for dilution of infusedfluids.

The use of such peripheral catheters avoids the complications associatedwith the direct puncture of the central venous circulation system andthey can remain in place for extended periods of time. However, due totheir longer length, smaller diameter and greater flexibility,peripheral catheters have not been used for rapid infusion measurementof central venous blood pressure or continuous central venous oximetry.

SUMMARY OF THE INVENTION

The present invention is a multilumen catheter which can be inserted viaa superficial (peripheral) vein into the central venous system for druginfusion, phlebotomy, rapid fluid infusion, hemodynamic pressuremonitoring and central venous oxygen saturation monitoring. Morespecifically, the catheter includes a sheath having a length anddiameter suitable for extending from a peripheral vein insertion pointto the superior vena cava of the patient and having two lumens formedtherein which extend from its proximal to its distal ends. A pair ofoptical fiber cables extend through one lumen and connect to an oxygensaturation measurement instrument at the proximal end, and a medicalinstrument such as a blood pressure monitor connects to the proximal endof the other lumen.

One object of the invention is to monitor central venous oxygensaturation using a peripherally inserted catheter. The peripheralinsertion results in the need for a substantially longer and moreflexible sheath while at the same time providing protection for thedelicate optical fibers used by the oxygen saturation measurementinstrument.

Another object is to provide a peripherally inserted catheter whichenables simultaneous measurement of central venous blood pressure andoxygen saturation. One lumen houses the optical fibers needed for oxygensaturation measurement, and the other lumen may be employed to monitorblood pressure in the central venous system.

Another aspect of the invention is the addition of a third lumen in thesheath which has a size sufficient to rapidly infuse fluids. Flow rateis increased by terminating the third lumen at a port in the sheathlocated at a point intermediate its ends. The port is located withrespect to the distal end of the sheath such that fluid flows into orproximal to the subclavian vein when the distal end of the sheath ispositioned in the superior vena cava.

The foregoing and other objects and advantages of the invention willappear from the following description. In the description, reference ismade to the accompanying drawings which form a part hereof, and in whichthere is shown by way of illustration a preferred embodiment of theinvention. Such embodiment does not necessarily represent the full scopeof the invention, however, and reference is made therefore to the claimsand herein for interpreting the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial pictorial view of the venous system of a humansubject;

FIG. 2 is a pictorial view of the preferred embodiment of the peripheralcatheter which employs the present invention;

FIG. 3 is a cross-sectional view of the catheter along the planeindicated at 3 in FIG. 2;

FIG. 4 is a cross-sectional view of the catheter along the planeindicated at 4 in FIG. 2;

FIG. 5 is a cross-sectional view of the catheter along the planeindicated at 5 in FIG. 2; and

FIG. 6 is a partial view in cross-section of the distal end of thecatheters of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring particularly to FIG. 1, the catheter 10 of the presentinvention is inserted into a superficial, or peripheral vein of apatient. The central venous system is comprised of the superior venacava 12 which extends downward into the right atrium of the heart (notshown in the drawings) and a set of veins which connect to it. Thesecentral venous system veins include the internal jugular vein 14, thesubclavian vein 18, the axillary vein 20 and brachial vein 24.

These central venous system veins lie deep beneath subcutaneous tissueand accompany large arteries. They are supplied with blood from anetwork of smaller, peripheral veins that extend throughout the limb ofthe patient and are located just under the skin (hence the term“superficial” veins). In the arm shown in FIG. 1, these peripheral veinsinclude the cephalic vein 22, the basilic vein 26 and cubital vein 28 inthe upper arm as well as the radial vein 30 and ulnar vein 32 in thelower arm. Some of these peripheral veins are better than others forinsertion of a catheter. Unlike the cephalic vein, the basilic vein doesnot collapse or kink with flexion of the deltoid and pectoral muscles,and is of larger caliber, providing a more favorable vein-to-catheterratio. Avoiding distal and intracubital placement improves patientperception of mobility for activities of daily living and avertscatheter “kinking” with arm flexion.

There are two requirements of a peripherally inserted central catheterwhich distinguish it from a central venous circulation (CVC) catheter.First, it is much longer. The distance from the superior vena cava 12from a typical subclavian insertion point is only 15 cm, whereas thedistance from a peripheral insertion point such as cephalic vein,basilic vein or cubital vein is from 40 to 60 cm.

The second major distinction is that the peripherally inserted cathetermust have more flexibility than a CVC catheter. The CVC catheter has arelatively short, straight run to the superior vena cava, whereas theperipheral catheter has a longer, more tortuous path. In addition, theperipheral veins are smaller in size and not as rigidly anchored inplace. Flexibility is required, therefore, in order to easily wind theperipheral catheter through the smaller, compliant peripheral veins.

The preferred embodiment of a peripherally inserted central catheter 10is shown in FIG. 2 and includes a sheath 50 made of a polyurethane basepolymer. It has a diameter of 5.0 to 5.3 French at its proximal end 52and is tapered to a smaller diameter at its distal end 54. The sheath 50is 55 cm in length and it has a radiopaque strip (not shown) along itsentire length for visualization with x-ray imaging systems. Polyurethaneoffers many advantages over other materials for the sheath 50.Polyurethane is a more durable material enabling the use of thinnerlumen walls. It offers less friction for ease of insertion; it isbiocompatible; it has good tensile properties for safe insertion withoutkinks or fractures; it is resistant to hydrolysis, oxidation, oils andthermal degradation; it is thromboresistant and non-hemolytic; and it isrigid at room temperature but softer at body temperature to become morepliant, flexible and kink resistant when inserted into a vein. It alsoallows better transduction of pressures than other materials.

Referring particularly to FIGS. 2 and 3, the first 30 cm of the catheter10 as measured from its proximal end 52 encloses three lumens 60, 62 and64. The lumens 60, 62 and 64 are formed by walls 66 integrally molded onthe interior of the sheath 50. The lumen 62 is the smallest in size andit is substantially centered inside the sheath 50. It houses two opticalfiber cables 70 and 72 which extend the entire length of the catheter 10as will be described in more detail below. The wall 66 surrounding lumen62 must be of sufficient thickness to protect the delicate opticalfibers 70 and 72 and prevent them from kinking when the catheter isbeing inserted.

The lumen 64 is a 20 gauge lumen which also runs the entire length ofthe catheter 10, and as will be described below, it may be used formeasuring blood pressure, drawing blood, infusing drugs, and guidewirehousing during insertion of the catheter 10.

The lumen 60 is the largest lumen in the sheath 50. It is 17 gauge andit extends from the proximal end 52 of the sheath 50 to an opening, orport, 80 in the sheath 50 located 30 cm from the proximal end 52. It isthus located 25 cm from the distal end 54, and when the catheter 10 isfully inserted with its distal end 54 located in the superior vena cava12, the port 80 is positioned within or proximal the subclavian vein 18.The large lumen 60 which the port 80 terminates thus provides a pathwayfor the infusion of fluids at a relatively high flow rate into thecentral venous system. Port 80 has a slit valve such as that disclosedin U.S. Pat. No. 5,810,789 and sold by CR Bard Inc. under the trademark“Groshong® valve”. The Groshong® valve opens inward for blood aspirationand outward for infusion but remains closed when not in use. Because thevalve remains closed when not in use, it seals the fluid inside thecatheter and prevents it from coming in contact with the patient'sblood. This closed ended system provided by the slit valve reduces therisk of blood reflux and air embolism. By maximizing the size of thelumen 60, increasing the size of the opening 80 and shortening the totallength of the lumen 60 (i.e., 30 cm instead of 55 cm) a dramaticincrease in fluid flow rate is achieved. In accordance with Poiseuille'sLaw:

Q=r ⁴ ΔP/8ηL

where:

Q=flow

r=internal lumen radius

ΔP=change in pressure

L=lumen length

η=constant.

Referring particularly to FIGS. 2 and 4, immediately distal the lumenopening 80 the internal configuration of the lumens housed by the sheath50 changes. The lumen 60 is no longer present, but the lumens 62 and 64continue on undisturbed. The outer diameter of the sheath 50 is alsounchanged at this point, but it gradually decreases in size as oneprogresses toward the distal end 54.

As shown best in FIGS. 2 and 5, at the distal end 54 of the sheath 50,the two lumens 62 and 64 terminate at openings in the tip of thecatheter 10. The ends of the optical fiber cables 70 and 72 are exposedat the tip in a manner such as that disclosed in U.S. Pat. No. 5,196,004so that light may be transported from the proximal end 52 in one opticalfiber cable 70 to blood surrounding the catheter tip 54 and reflectedlight may be transported back to the proximal end 52 through the otheroptical fiber cable 72. As will be described below, this opticalinformation is used to monitor central venous oxygen saturation. Thelumen 64 extends through the distal end 54 and a port 65 is formed tocommunicate with surrounding blood as shown in FIG. 6. The outerdiameter of the sheath 50 is reduced substantially at the distal end 54to enhance the flexibility of the catheter and facilitate its insertion.

Referring particularly to FIG. 2, the three lumens 60, 62 and 64 areterminated at the proximal end 52 of the sheath 50 by a cathetermanifold 90 such as that disclosed in U.S. Pat. No. 4,670,009 which isincorporated herein by reference. The catheter manifold 90 connects thelumens 60, 62 and 64 to respective catheter extension tubes 92, 94 and96. The optical fiber cables 70 and 72 extend into the catheterextension tube 94 and terminate in a connector portion of aconnector/receptacle 98 such as that described in U.S. Pat. No.5,007,704 which is incorporated herein by reference. The receptacleportion of the connector/receptacle 98 forms part of an oxygensaturation measurement instrument 100 such as that described in U.S.Pat. No. 4,651,741 which is also incorporated herein by reference. Theoxygen saturation instrument 100 measures oxygen saturation in bloodflowing past the distal tip of the catheter 10 by detecting the relativereflectivity of the blood under red illumination and infraredillumination. The intensity signal λ₁ of red light reflected by bloodback through optical fiber cable 72 is measured, as is the intensitysignal λ₂ of the reflected infrared light. The intensity ratio I=λ₂/λ₁is used to calculate oxygen saturation of the blood.

The catheter extension tubes 92 and 96 are terminated with connectors102 and 104 which enable them to be connected to a number of differentdevices. Connector 102 is shown connected to a syringe 108. The syringemay be operated to infuse at a high flow rate a fluid through the largecatheter lumen 60 to opening 80 aligned within or proximal to thesubclavian vein 18. Such fluids might be, for example, resuscitationcrystalloid, colloids, blood products or intravenous contrast.

The connector 104 is shown connected to a blood pressure monitorinstrument 110. An instrument 110 such as that commercially availablefrom Maxxim, Inc. under the trade name “CDXpress® transducer” may beused for this purpose. This is a continuous infusion transducer devicein which a low constant flow of saline solution, or heparinized salinesolution is pumped through the lumen 64 and out its distal opening atthe tip of the catheter 10. A flow rate of 3 mL/hr is all that isrequired to flush the lumen 64 and insure that the blood pressure at thetip of the catheter 10 is accurately reflected through the lumen 64 to apressure transducer (not shown) in the monitor 110.

Referring particularly to FIGS. 1 and 2, the catheter 10 is inserted inthe patient through a peripheral vein in the arm (e.g., basilic,cephalic or cubital veins). A 1.88″, 20 Gauge intravenous catheter isinserted in the peripheral vein and a 30 cm long, 0.018″ diameter springguidewire is passed through the intravenous catheter leading to thecentral venous system. The intravenous catheter is then removed and a5.0-5.5 French sheath introducer and dilator unit (e.g., such as thatsold by HDC Corporation under the trademark V=cath Safe-T-Peel”® or thatsold by Cook Critical Care under the trademark Peel-Away Cook®) isinserted over the guidewire. The guidewire and dilator are removedleaving the introducer in the peripheral vein. The catheter 10 is theninserted through the introducer and guided into the central venouscirculation terminating in the superior vena cava. As shown in FIG. 6,the catheter 10 is preloaded with a 0.025″ diameter removable guidewire112 that passes through connector 104, extension 96 and lumen 64terminating proximal the catheter tip 54. The guidewire 112 providesincreased catheter stiffness during the insertion process. Theintroducer sheath is split and peeled away from the catheter 10 onceinsertion is complete. Upon confirmation of catheter position with achest X-ray, the preloaded removable guidewire 112 is withdraw andconnector 104 is fastened to the pressure monitor 110. A securing devicesuch as that sold by Arrow International under the trademark “Statlock®”may be used at the insertion site to prevent catheter dislodgement ormigration.

When fully inserted the catheter 10 may be used to perform a number offunctions. The central venous oxygen saturation (S_(cv)O₂) is monitoredby instrument 100 and the venous blood pressure is monitored byinstrument 110. Any fluids that need to be introduced into the centralvenous system may be injected using syringe 108 or an infusion pump (notshown in drawing). Because of its peripheral insertion, the catheter 10may remain in place and fully functional for months.

It should be apparent that variations in the preferred embodimentdescribed above are possible without departing from the spirit of theinvention. For example, 55 cm is an optimal length for the peripheralcatheter for insertion in the best peripheral veins in the upper arm,but lengths ranging from 35 cm to 65 cm are useful for peripheralinsertion. Similarly, a range of sheath diameters are possible, but forperipheral insertion the diameter should not exceed 5.5 French. Also,other devices can be connected to and use the two lumens 60 and 64. Forexample, infusion pumps, radiocontrast power injectors, and pressurebags for lumen 60 and syringes or infusion pumps for lumen 64. Also,while in most procedures it is sufficient to extend the distal tip ofthe catheter into the superior vena cava, it will be understood by thoseskilled in the art that the catheter tip may also be extended into theright atrium of the patient's heart. Structurally, no changes in thecatheter are required to do this, although another 5 to 10 cm of lengthmay be helpful.

What is claimed is:
 1. A peripherally inserted central venous systemcatheter which comprises: a sheath having a length and a diametersuitable for extending from a peripheral vein insertion point on apatent to the superior vena cava of the patient, the sheath beingconstructed of a material suitable for insertion into the venous systemof a subject through a peripheral vein and forming two lumens thereinwhich extend from its proximal end at the insertion point to its distalend in the superior vena cava; a pair of optical fiber cables disposedin one of the lumens and extending from the distal end to the proximalend of the sheath; a connector fastened to the proximal ends of the twooptical fiber cables for connecting them to an oxygen saturationmeasurement instrument; and a second connector fastened to the proximalend of the other of said two lumens for connecting the second lumen to amedical instrument, wherein central venous oxygen saturation of thepatient's blood is measured and a medical procedure is simultaneouslyperformed using the medical instrument.
 2. The catheter of claim 1 inwhich the medical instrument is a blood pressure monitor which measuresblood pressure at the distal end of the sheath.
 3. The catheter asrecited in claim 1 in which the sheath has a length greater than 35 cm.4. The catheter as recited in claim 3 in which the sheath has a diameterless than 5.5 French.
 5. The catheter as recited in claim 1 in which thesheath is formed from a polyurethane base polymer.
 6. A peripherallyinserted central venous system catheter which comprises: a sheath havinga length and a diameter suitable for extending from a peripheral veininsertion point on a patent to the superior vena cava of the patient,the sheath being constructed of a material suitable for insertion intothe venous system of a subject through a peripheral vein and forming twolumens therein which extend from its proximal end at the insertion pointto its distal end in the superior vena cava; a pair of optical fibercables disposed in one of the lumens and extending from the distal endto the proximal end of the sheath; a connector fastened to the proximalends of the two optical fiber cables for connecting them to an oxygensaturation measurement instrument; and a second connector fastened tothe proximal end of the other of said two lumens for connecting thesecond lumen to a medical instrument, wherein central venous oxygensaturation of the patient's blood is measured and a medical procedure issimultaneously performed using the medical instrument; and in which athird lumen is formed in the sheath and extends from its proximal end toa point intermediate the ends of the sheath where it communicates withblood surrounding the sheath through a port formed in the sheath; and athird connector is fastened to the proximal end of the third lumen forconnecting the third lumen to a fluid infusion device; wherein the thirdlumen is larger than said two lumens such that fluids may be infusedinto the central venous system of the patient through said port.
 7. Thecatheter of claim 6 in which the medical instrument is a blood pressuremonitor which measures blood pressure at the distal end of the sheath.8. The catheter as recited in claim 6 in which the sheath has a lengthgreater than 35 cm.
 9. The catheter as recited in claim 8 in which thesheath has a diameter less than 5.5 French.
 10. The catheter as recitedin claim 6 in which the sheath is formed from a polyurethane basepolymer.